Process for the manufacture of aliphatic monocarboxylic acids from alkyl sulfuric acids



United States Patent 3,261,856 PROCESS FOR THE MANUFACTURE OF ALI- PHATIC MONOCARBOXYLIC ACIDS FROM ALKYL SULFURIC ACIDS Jonas Kamlet, deceased, late of New York, N.Y., by Edna Yadven Kamlet, executrix, New York, N.Y., assignor to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio N0 Drawing. Filed Dec 27, 1962, Ser. No, 247,763 4 Claims. (Cl. 260-413) This invention relates to the production of aliphatic monocarboxylic acids and has for its general object the provision of a process for the production of aliphatic monocarboxylic acids from alkyl sulfuric acids and their salts. More particularly, the invention provides for a process whereby aliphatic monocarboxylic acids, containing from about two to about twenty-one carbon atoms, are produced from the sulfation products of relatively inexpensive and plentiful raw materials, for example, the alpha olefines. Specifically, the invention provides for a process whereby sulfated products of alpha olefines can be converted into fatty monocarboxylic acids which have utility as base products for detergent manufacture, plasticizer precursors and foam depressants. Shortchain monocarboxylic acids, which have utility as reagents in the manufacture of esters, salts and plastics can also be recovered.

Aliphatic monocarboxylic acids, characterized by the presence of one carboxylic group attached to an aliphatic carbon chain, have been found to be widely distributed in nature. For example, they occur in a wide variety of fats, oils and waxes in the form of triglycerides. These naturally occurring aliphatic monocarboxylic acids, almost without exception, have an even number of carbon atoms and are straight-chain acids. In addition to their natural occurrence, a number of methods are known for the industrial preparation of the aliphatic monocarboxylic acids. These methods include the oxidation of primary alcohols, or aldehydes, and the hydrolysis of nitriles, esters, amides, acid chlorides and acid anhydrides.

The most widely accepted source of aliphatic monocarboxylic acid raw materials of the longer chain lengths has been their natural forms occurring in animal fats, nut means and the like materials. These natural sources limit the industrial application of the higher chain length monocarboxylic acids by subjecting industrial users to the necessity and uncertainty of obtaining raw materials from growth sources. In contrast, the novel process .of the present invention provides means whereby adequate supplies of quality aliphatic monocarboxylic acids having odd or even chain lengths can be produced at relatively low and stable prices.

It is, therefore, an object of this invention to provide a process whereby alkyl sulfuric acids and their watersoluble salts derived from alpha olefines are converted into long and short-chain aliphatic monocarboxylic acids.

It is a further object of this invention to provide a process whereby derivatives of alpha olefines are converted into aliphatic monocarboxylic acids having at least one less carbon atom than the alpha olefine raw material.

These objects are achieved by the present invention which is directed to a process for the conversion of derivatives of alpha olefines having about 8 to about 22 carbon atoms into aliphatic monocarboxylic acids having about 2 to about 21 carbon atoms, wherein the major portion of the aliphatic monocarboxylic acids produced are found to have 1 to about 4 less carbon atoms than their alpha olefine precursors.

Applicant has discovered that the conversion can be effected in excellent yield to produce quality acids by sub- 3,261,856 Patented July 19, 1966 jecting the initial alpha olefines to a series of processing steps comprising the following, wherein step 1 is a preliminary step and steps 2 and 3 are essential steps of the Baron, granted July 10, 1934; United States Patent No.

1,991,948 to Kenneth B. Lacy, granted February 19, 1935; United States Patent No. 2,027,896 to Heinrich Bertsch, granted January 14, 1936; United States Patent No. 2,028; 226 to Robert F. Le Baron, granted January 21, 1936; and United States Patent No. 2,135,358 to Chester Merle Suter, granted November 1, 1938, to result in a reaction product consisting primarily of alkyl sulfuric acids having the sulfuric acid ester group attached to the second carbon atom (2-alkylsulfuric acids);

(2) Treating the alkyl sulfuric acid reaction product of step 1, or the water soluble salts thereof formed by neutralization with water-soluble hydroxides, with an oX- idizing reagent, for example, nitric acid, with or without the addition of oxidizing catalysts, whereby the alkyl sulfuric acids are cleaved and oxidized to result in a mixture of aliphatic monocarboxylic acids together with byproducts which may include nitrogenous compounds when I-INO is used as the oxidizing reagent; and

(3) Recovering the aliphatic monocarboxylic acids, together with any nitrogenous compounds formed in step 2, by conventional distillation or extraction procedures and, if nitrogen containing by-products are produced in step 2 and their removal is desired, removing them by, for example, digesting .the crude monocarboxylic acid products with hydrochloric acid or another non-oxidizing mineral acid at advanced temperatures.

Suitable sources for the terminal or alpha olefine raw materials for use in the first step of the present process are, for example, the cracked products of branched or straight-chained parafiins. The olefine raw materials can also be obtained from the polymerization of ethylene in the presence of organo-aluminum catalysts as disclosed in the United States Patent to Karl Ziegler and Hans George Gilbert, No. 2,695,327, granted November 23, 1954, and the United States Patent to Karl Ziegler, Gunther Wilke and Erhard Hozlkarnp, No. 2,781,410, granted February 12, 1957. The isomerization route for the conversion of higher internal olefines to lower terminal olefines via the organo-borane route reported by Brown and Subba Rao, American Chem. Soc. J. 81 (1959), pp. 64236428, and pp. 6434-6437, also provides suitable alpha olefine raw materials.

As stated above, applicant has found that conventional methods with any convenient sulfating agent can be employed to carry out the sulfation of the terminal olefines. For practical and economic reasons, however, sulfuric acid is preferred as the sulfating agent. Also, a sulfation procedure which maximizes the 2-alkyl sulfuric acid content of the sulfation product is preferable, if an optimum yield of fatty monocarboxylic acids is desired.

As stated hereinbefore, the sulfation of alpha olefines results in a mixture of alkyl-sulfuric acids. A typical sulfation product, derived from the sulfation of an alpha olefine, or mixtures thereof, contains a predominant percentage of alkyl sulfuric acid wherein the sulfuric acid ester group is attached to the second carbon atom and a minor percentage wherein the sulfuric acid ester group is attached to the third carbon atom. Still lesser percentages of isomers wherein the sulfuric acid ester group is attached to a more internal carbon atom are formed.

For example, the product resulting from the sulfation of one mole of an alpha olefine containing twelve carbon atoms with about 2 moles of 98% sulfuric acid at about 20 C. for about minutes, consists essentially of a mixture of alkyl sulfuric acids wherein approximately 80% of the sulfuric acid ester groups are attached to the second carbon, approximately of the sulfuric acid ester groups are attached to the third carbon and approximately 5% of the sulfuric acid ester groups are attached to more internal carbon atoms.

The second step of the present process, the oxidation step, can be carried out by adding the alkyl sulfuric acids to an agitated aqueous solution of nitric acid having a concentration of at least about and preferably between about and about 35%, with or without the presence of a water miscible, non-reactive organic solvent. The aqueous solution of nitric acid can contain a maximum of about 65% of sulfuric acid provided that the solution contains at least about 20% of nitric acid as stated above. The volume of nitric acid solution employed initially is such that about 3 to about 20 moles, preferably about l5 moles, of nitric acid per mole of alkyl sulfuric acids are present. Additional amounts of concentrated nitric acid are added if necessary to maintain a nitric concentration of at least about 20%, and a total of up to about 54 moles of nitric acid per mole of alkyl sulfuric acids have been used in the oxidation reaction. Equivalent amounts of nitrogen dioxide can also be employed to effect oxidation.

If the water-soluble salts of the alkyl sulfuric acids are employed, their concentration in an aqueous or non-reactive solvent solution for use in the oxidation reaction is not deemed critical, although the solutions should be mobile and should not contain excess amounts of Water to dilute the oxidizing reagent. For instance, the water soluble salts of the alkyl sulfuric acids can be employed at concentrations of about 20% to about 60% by weight in aqueous solutions or slurries.

As indicated above, the salts of the alkyl sulfuric acids herein described, as well as the acids, can be subjected to treatment with the oxidizing agent to form the monocarboxylic acid derivatives. Therefore, it is to be understood that statements hereinafter relating to the treatment of the acids are also intended to apply to the treatment of their water-soluble salts.

Although the oxidation reaction will take place in the absence of catalysts, copper, manganese dioxide, ammonium vanadate, benzoyl peroxide, vanadium pentoxide, cobaltic oxide, and mixtures thereof are effective when employed in amounts between about 0.005% and about 5.0% based on the weight of the alkyl sulfuric acids entering into the oxidizing reaction. These catalysts increase the yield of monocarboxylic acids, decrease the nitrogen content of the monocarboxylic acid products and render any nitrogen containing by-products more susceptible to removal. Of the catalysts enumerated above, a combination of 0.75% of powdered copper together with about 0.25% of ammonium vanadate based on the Weight of the alkyl sulfuric acids has particular advantage and about 1.2% of vanadium pentoxide on the same basis is most desirable.

The alkyl sulfuric acids are added to the agitated nitric acid oxidizing solutions at such a rate that the temperature is maintained between about 50 C. and the reflux temperature of the reacting mass. The reaction temperature is generally maintained at about 50 C. to about 140 C., and a reaction temperature of about 80 C. to about 115 C. is preferred. The oxidation temperature can be maintained by adjusting the rate of alkyl sulfuric acid addition. Cooling may be provided, if desired, so that the rate of reactant addition can be increased. However, provision may have to be made to handle foaming which may result from the increased reaction rate. The oxidation reaction is terminated when gas evolution ceases. I

After completion of the oxidation, recovery of desired monocarboxylic acids is effected; the liquid reaction mass can be allowed to stratify and separate into:

(1) A lower aqueous layer, containing short-chain, water-soluble monocarboxylic acids, any excess oxidizing agent, the catalyst, water-soluble side products, and

(2) An organic layer, containing fatty Water-insoluble monocarboxylic acids and water-insoluble byproducts. Both of these product layers may contain small and variable amounts of nitrogenous materials.

A water-miscible, non-reactive solvent diluent, for example, dimethyl sulfoxide, can be added to the reaction mass to promote oxidation and to suppress nitration. The use of a solvent diluent can also have the effect of trapping nitrogen-containing byaproducts in the aqueous layer. Therefore, the addition of water miscible, non-reactive solvents provides a means of reducing the nitrogen content of the fatty monocarboxylic acid product.

The oxidation step proceeds exothermically to a typical completeness of about 46% to about 88% in terms of the moles of water-insoluble monocarboxylic acids produced per mole of olefine raw material, and about 48% to about 91% in terms of the moles of water-insoluble monocarboxylic acids produced per mole of alkyl sulfuric acid isomers. One mole of short-chain, watersoluble monocarboxylic acid is theoretically produced for each mole of water-insoluble monocarboxylic acid. These short-chain monocarboxylic acids are found in the water-soluble layer, and, with the exception of formic acid which decomposes, they can be recovered by conventional distillation and extraction methods.

During the oxidation step of the present process, cleavage of the carbon chain of a 2-alkyl sulfuric acid occurs predominantly on the long chain side of the carbon to which the sulfuric acid ester group is attached. As the point of sulfuric acid ester attachment shifts to the third and fourth carbon of the alkyl group, the cleavage occurs more equally on both sides of the point of attachment. Since cleavage can, and does, occur on either side of the carbon containing the sulfate group, a 2-alkyl sulfuric acid produces monocarboxylic acids according to the partial reaction outline shown below.

In the formulas set forth above R is a straight or branched-chain aliphatic group having from 5 to 19 carbon atoms. With all possible isomers reacting in a mixture of alkyl sulfuric acids derived from alpha olefines of the specified chain lengths, monocarboxylic acids, whose carbon chains have from one less carbon atom than the original olefine down to those having two carbon atoms, are produced. No single carbon monocarboxylic acid, formic acid, is recovered because this acid decomposes in the reaction to form carbon dioxide gas and Water.

In one experimental run, for example, the monocarboxylic acid products resulting from the oxidation of essentially pure 2-alkyl sulfuric acids derived by sulfating C olefine had the following typical product distribution.

Carbon chain lengths Wei ht ercenta e in monocarboxylic acid g p g of monocarboxylic acid Gaseous products are also evolved during the oxidation step. These gaseous products include carbon dioxide from decomposition of short-chain monocarboxylic acids and various oxidized nitrogen gases including NO, N0 and N 0.

The water-insoluble layer resulting from the oxidation step can be analyzed by chemical analyses including determinations of the acid value (A.V.), the saponification value (S.V.), the hydroxyl value (H.V.) and the Kjeldahl nitrogen percentage. Infrared, distillation, and gas chromatographic methods can also be employed in the examination of the fatty acid products.

Since the presence of nitrogen compounds in the product monocarboxylic acids may be deterimental to certain properties including the odor and color stability of products in which they are subsequently used, practice of the present process preferably includes precautions to minimize formation of nitrogen compounds. If the separation of nitrogen com-pounds from the product monocarboxylic acids is desired, several alternative process steps can be employed.

For reasons of economy and efliciency, removal of the nitrogen compounds by hydrolysis with hydrochloric acid at elevated temperatures, as detailed below, is preferred. In general the preferred process consists of hydrolyzing the nitrogenous compounds in the crude acids with hydrochlon'c acid having a concentration of about 20% to about 40% at temperatures of up to-250 C. for periods of about 2 to about 8 hours. It has been found preferable to carry out the hydrolysis by mixing the crude fatty monoca-rboxylic acids from the oxidation step with an approximately equal volume of 37% hydrochloric acid and agitating the mixture for about 5 hours at temperatures of about 175 C. to about 250 C. Very little acid is consumed, only sufiicient acid for good contact is actually required, and about 92% of the nitrogen present in the water-insoluble monocarboxylic acids is removed.

After hydrolysis, the m-onocarboxylic-hydroch-loric acid mixture is allowed to stratify to form an upper organic phase and a lower aqueous phase. The upper phase containing the fatty monocarboxylic acids is then separated. The fatty monoca-rboxylic acids are removed from the separated upper organic phase by conventional extraction or distillation procedures.

Nitrogen removal can also be effected by a sulfuric acid hydrolysis wherein an approximately equal volume of sulfuric acid having a concentration of about 20% to about 80% is added to the water-insoluble monocarboxylic acids. The mixture is then heated to a temperature between about 80 C. and about 150 C. for periods of about 2 to about 6 hours. Mechanical agitation is provided during the heating period to insure contact between the sulfuric acid and the mon-ocarboxylic acids. This purification method removes about to about 50% of any nitrogen compounds present in the monocarboxylic acids.

Another method of ridding the fatty mon-ocar-boxylic acid products of their nitrogen content includes converting the acids to their methyl esters by treatment with an excess of methanol in the presence of a catalytic amount of sulfuric acid, e.g., about 2% by weight of the methanol. The methyl esters are then recovered by either evaporating off the methanol and then distilling off the methyl esters or, (1) extracting the crude methyl fatty acid esters with petroleum ether, (2) evaporating off the petroleum ether, (3) add-ing about 10% by weight of concentrated sulfuric acid to the solvent-free extract, and (4) distilling off the methyl esters of the fatty mono-carboxylic acids. This purification method results in essentially nitrogenfree methyl esters which, if desired, can be converted by conventional means to nitrogen-free fatty monocarboxylic acids.

Another effective scheme for removal of nitrogen compounds involves a mild neutralization of the crude fatty monocarboxylic acids followed by a mild reacidification of the resulting soap solution. For example, this denitrification procedure can be carried out at room temperature by the addition of suflicient aqueous sodium hydroxide solution, having a concentration of about 5%,

to the crude fatty monocarboxylic acids to result in a pH of about 9. This mixture is allowed to stratify into an upper water-insoluble phase and a lower water-soluble phase which contains the sodium salts of the fatty monocarboxylic acids. In order to recover the fatty monocarboxylic acids, this water-soluble phase is separated and by the addition of sufiicient hydrochloric acid, having a concentration of about 5%, to result in a pH of about 2, about of the nitrogenous materials remain in the upper water-insoluble phase formed after the addition of sodium hydroxide. This nitrogen removal method is preferably carried out at a temperature below about 32 C. The neutralization pH in .this method of de-nitrification is between about 8 and about 11, and the reacidi-fication is carried out at a pH between about 2 and about 6.

The practice of the invention is described more particularly in the following examples, but it will be understood that limitation of the scope of the invention is not thereby intended.

Example I An aqueous slurry containing approximately 22% by weight of the sodium salts of C alkyl sulfuric acids derived from C alpha olefine was added slowly, over a period of 155 minutes, to an aqueous solution containing 30% by weight of nitric acid. The nitric acid solution was preheated to a temperature of 80 C. The initial volume of the nitric acid solution was such that one mole of the alkyl sulfuric acid salts was added per 11.5 moles of nitric acid, and the addition was made at a rate which maintained the oxidation temperature at 80 C. A catalyst, consisting of 0.54% of powdered copper together with about 0.18% of ammonium vanad-ate based on the weight of the alkyl sulfuric acid salts, was added to the aqueous solution of nitric acid prior to adding the alkyl sulfuric acid salts. Mechanical agitation and refluxing were provided during the oxidation and 11.5 moles of additional nitric acid per mole of alkyl sulfuric acid salts were added to the reaction mass as an aqueous solution containing 70% by weight of nitric acid to maintain the nitric acid concentration above 20%. The oxidation was terminated when gas evolution ceased, and the product, recovered as a fatty acid containing water-insoluble upper layer after stratification of the reacted mixture, exhibited an AV. of 226 and a nitrogen content of 1.56%. Watersoluble short-chain length monocarboxylic acids were present in the lower aqueous phase. The molar yield of water-insoluble fatty monocarboxylic acid was 54.5% based on the moles of alkyl sulfuric acid salts entering the reaction.

In another run, under substantially the same conditions as those of the process of Example I above, with the exception of the oxidation temperature, which was C. and the addition time of the alkyl sulfuric acid salts which was 45 minutes, the fatty acid containing water-insoluble layer had an AV. of 240 and a nitrogen content of 1.53%. The molar yield of the water-insoluble fatty monocarboxylic acids in this run was 62.4% based on the moles of alkyl sulfuric acid salts entering the reaction.

The fatty acids produced by the process of Example I are useful in the production of soap for detergent purposes.

Example 11 An aqueous slurry containing approximately 40% by weight of the sodium salts of C alkyl sulfuric acids .derived from C alpha olefine was added slowly, over a period of 45 minutes, to an aqueous solution containing 20% by Weight of nitric acid and preheated to 80 C. The initial volume of the nitric acid solution was such that one mole of the alkyl sulfuric acid salts was added per 4.75 moles of nitric acid. The addition was made at a rate which maintained the oxidation temperature at 80 C. A catalyst, consisting of 0.75% of powdered copper together with about 0.25% of ammonium vanadate based on the weight of the alkyl sulfuric acids salts, was added 7 to the aqueous solution of nitric acid prior to adding the alkyl sulfuric acid salts. As in the process of Example I above, mechanical agitation and refluxing were provided during the oxidation. An additional 4.85 moles of nitric acid per mole of alkyl sulfuric acid salts were added to the reaction mass as an aqueous solution containing 70% by Weight of nitric acid during the oxidation to maintain the nitric acid concentration above 20%. The oxidation was terminated when gas evolution ceased and the product, recovered as a fatty acid containing water-insoluble upper layer after Stratification of the reacted mixture exhibited an A.V. of 122, an H.V. of 82 and a nitrogen content of 1.49%. As in the process of Example I above, water-soluble short-chain length monocarboxylic acids were present in the lower aqueous phase. The fatty acid products produced by the process of this example are imminently suitable for saponification and use as soaps.

Example III An aqueous slurry containing approximately 60% by weight of the sodium salts of C alkyl sulfuric acids derived from C alpha olefine was slowly added, over a period of approximately 21. minutes, to an aqueous solution containing 30% by Weight of nitric acid and preheated to 100 C. The initial volume of the nitric acid solution was such that one mole of the alkyl sulfuric acid salts was added per 6.85 moles of nitric acid. The addition was made at a rate which maintained the oxidation temperature at 100 C. No catalyst was employed in this reaction. Mechanical agitation and refluxing were provided during the oxidation and an additional 9.35 moles of 70% nitric acid per mole of alkyl sulfuric acid salts were added to the reaction mass during the oxidation. The oxidation was terminated when gas evolution ceased, and the product, recovered as a fatty acid-containing water-insoluble upper layer after stratification of the reacted mixture, exhibited an A.V. of 174, an H.V. of 73 and a nitrogen content of 1.57%. The lower aqueous phase contained short-chain length monocarboxylic acids formed during the oxidation.

The fatty acid products produced by the process of this example are excellently suited for use as lather modifying agents in soaps and surfactants. The short-chain length monocarboxylic acids are useful reagents in the manufacture of organic salts, esters and plastics.

Example IV An aqueous slurry containing approximately 60% by weight of the sodium salts of C alkyl sulfuric acids derived from C alpha olefine was slowly added, over a period of 127 minutes, to an aqueous solution containing 92% by weight of nitric acid and preheated to 100 C. The initial volume of the nitric acid solution was such that one mole of the alkyl sulfuric acid salts was added per 37.1 moles of nitric acid. The addition of the alkyl sulfuric acid salts was made at a rate which maintained the oxidation temperature at 100 C. A catalyst, consisting of 0.9% of powdered copper together with about 0.297% of ammonium vanadate based on the weight of alkyl sulfuric acid salts, was added to the aqueous solution of nitric acid prior to adding the alkyl sulfuric acid salts. Mechanical agitation and refluxing were provided during the oxidation, and 16.4 moles of additional nitric acid per mole of alkyl sulfuric acid salts were added to the reaction mass as an aqueous solution containing 70% by weight of nitric acid during the oxidation. The oxidation reaction was terminated when gas evolution ceased, and the product, recovered as a fatty acid-containing waterinsoluble upper layer, after stratification of the reacted mixture exhibited an A.V. of 294, an H.V. of 17 and a nitrogen content of 1.91%.

Example V An aqueous slurry containing approximately 20% by weight of the sodium salts of C alkyl sulfuric acids de- & rived from C alpha olefine was slowly added, over a period of 32 minutes, to an aqueous solution containing by weight of nitric acid and preheated to a temperature of 110 C. The initial volume of the nitric acid solution was such that one mole of the alkyl sulfuric acid salts was added per 13.7 moles of nitric acid. The addition of the alkyl sulfuric acid salts was made at a rate which maintained the oxidation reaction at the preheat temperature. The catalyst employed in the process of this example was identical to that of the process of Example IV above. As in the previous examples, mechanical agitation and refluxing were provided during the oxidation. During the oxidation, 21 moles of additional nitric acid per mole of alkyl sulfuric acid salts were added to the reaction mass as an aqueous solution containing 70% by weight of nitric acid to maintain the nitric acid concentration in the oxidation above 20%. The oxidation was terminated when gas evolution ceased, and the product, recovered as a fatty acid-containing water-insoluble upper layer, after Stratification of the reaction mixture, exhibited an A.V. of 240 and a nitrogen content of 2.54%. Short-chain monocarboxylic acids were present in the lower aqueous layer after Stratification of the oxidation mixture. The fatty acid products produced by the process of this example are excellently suited for use as raw materials in the preparation of acyl monoand diethanolamides which are known builders for synthetic detergents.

Example VI An aqueous slurry containing approximately 30% by weight of the sodium salts of C alkyl sulfuric acids derived from C alpha olefine was slowly added, over a period of 17 minutes, to an aqueous solution containing 25% by weight of nitric acid and 63% by weight of sulfuric acid. The temperature of this oxidation reaction was 120 C., maintained by the addition of alkyl sulfuric acid salts after initially preheating the nitric-sulfuric acid solution. As in the process of Example V above, the oxidation catalyst employed was 1.5 of powdered copper together with about 0.5% of ammonium vanadate based on the weight of the alkyl sulfuric acid salts added to the oxidation mixture. Mechanical agitation and refluxing were provided during the oxidation step and 10.8 moles of additional nitric acid per mole of alkyl sulfuric acid salts were added to the reaction mass as an aqueous solution containing 70% by weight of nitric acid during the oxidation. When gas evolution ceased, the product, recovered as a fatty acid-containing water'insoluble upper layer after Stratification of the reacted mixture, exhibited an A.V. of 257, an H.V. of 6 and a nitrogen content of 1.10%.

Other water soluble salts of alkyl sulfuric acids such as the magnesium and potassium salts can be used in place of the sodium salts of this example to result in the production of monocarboxylic acids.

Example VII An aqueous slurry containing approximately 41.5% by weight of the sodium salts of C alkyl sulfuric acids derived from C alpha olefine was slowly added, over a period of 55 minutes, to an aqueous solution containing 30% by weight of nitric acid and preheated to C. The initial volume of the nitric acid solution was such that one mole of the alkyl sulfuric acid salts was added per 7.32 moles of nitric acid. The addition was made at a rate which maintained the oxidation temperature at C. A catalyst, consisting of 0.535% of vanadium pentoxide based on the weight of the alkyl sulfuric acid salts was added to the aqueous solution of nitric acid prior to adding the alkyl sulfuric acid salts. As in the foregoing examples, mechanical agitation and refluxing were provided during the oxidation. 9.38 moles of additional 70% nitric acid per mole of alkyl sulfuric acid salts were added to the reaction mass during oxidation to maintain the nitric acid concentration above 20%.

When the gas evolution ceased, the mechanical agitation was stopped and the reaction mixture was allowed to stratify. The fatty acid-containing water-insoluble upper layer which formed exhibited an A.V. of 271, an H.V. of 0, an S.V. of 317 and a nitrogen content of 1.06%.

The substitution of the sodium salts of C alkyl sulfuric acids derived from C alpha olefine in the process of Example VII results in the formation of monocarboxylic acids containing from 2 to 7 carbon atoms.

Example VIII Sodium salts of C alkyl sulfuric acids derived from C alpha olefine were added to an aqueous nitric acid solution as a slurry according to the process of Example I. The addition was made over a period of 6 minutes. The initial concentration of the nitric acid solution was 30%, and the solution temperature was 95 C. The initial volume of the nitric acid solution was such that one mole of the alkyl sulfuric acid salts was added per 9.55 moles of nitric acid. A catalyst, consisting of 2.66% of benzoyl peroxide based on the weight of the alkyl sulfuric acid salts entering the reaction was added to the aqueous solution of nitric acid prior to the addition of the alkyl sulfuric acid salts. Mechanical agitation and refluxing were provided during the oxidation and 12.95 moles of additional 70% nitric acid per mole of alkyl sulfuric acid salts were added to the reaction mass as an aqueous solution containing 70% by weight of nitric acid to maintain the nitric acid concentration above 20% during the reaction termination of the oxidation and stratification of the reaction mass, the upper water-insoluble layer was found to contain fatty monocarboxylic acids. The fatty acidcontaining water-insoluble upper layer exhibited an A.V. of 198, an H.V. of 23 and a nitrogen content of 2.23%.

The molar yield of water-insoluble fatty moncarboxylic acids was 47.2% based on the moles of alkyl sulfuric acid salts entering the reaction. Monocarboxylic acids are also produced when the oxidation temperature maintained in the process of Example VIII is the reflux temperature of the oxidation mixture.

Example IX Sodium salts of C alkyl sulfuric acids derived from C alpha olefine were added slowly, over a period of 25 minutes, to an aqueous solution of nitric acid having an ployed in the process of this example was 0.75% of copper powder based on the weight of the alkyl sulfuric acid salts entering the reaction. The oxidation reaction was carried out with provision for mechanical agitation and refluxing as in the previous examples, and 12.94 moles of additional nitric acid per mole of alkyl sulfuric acid salts were added to the reaction mass as an aqueous solution containing 70% by weight of nitric acid to maintain the nitric acid concentration above 20%. As before, the oxidation was terminated when gas evolution ceased, and the product, recovered as a fatty acid-containing waterinsoluble upper layer after stratification of the reacted mixture, exhibited an A.V. of 234, an H.V. of 29 and a nitrogen content of 1.49%. The molar yield of waterinsoluble fatty monocarboxylic acids was 565% based on the moles of alkyl sulfuric acid salts entering the reaction. The fatty monocarboxylic acids resulting from the process of Example IX were converted into nitrogen-free methyl esters by treating the crude acids with an excess of methanol containing 2% by weight of sulfuric acid, extracting the resulting methyl esters with petroleum ether, evaporating off the petroleum ether solvent, adding by weight of sulfuric acid to the crude methyl esters and 10 vacuum distilling essentially nitrogen-free methyl esters of the fatty monocarboxylic acids.

Example X An aqueous slurry containing approximately 20% by weight of the sodium salts of C alkyl sulfuric acid derived from C alpha olefine was slowly added, over a period of approximately -54 minutes, to an aqueous solution containing 30% by weight of nitric acid and preheated to C. The initial volume of nitric acid solution was such that one mole of the alkyl sulfuric acid salts was added per 19.4 moles of nitric acid. The addition was made at a rate which maintained the oxidation temperature at 105 C. A catalyst, consisting of 5% manganese dioxide based on the weight of the alkyl sulfuric acid salts was added to the aqueous solution of nitric acid prior to adding the alkyl sulfuric acid salts. Mechanical agitation and refluxing were provided during the reaction, and no additional nitric acid was added to the reaction mass. The oxidation was terminated when gas evolution ceased, and the product, recovered as a fatty acidcontaining water-insoluble upper layer after stratification of the reacted mixture exhibited an A.V. of and a nitrogen content of 2.02%. The molar yield of waterinsoluble fatty monocarboxylic acids was 45.6% based on the moles of alkyl sulfuric acid salts entering the reaction.

Comparable results are obtained in the process of Example X when the initial concentration of the nitric acid solution is 35%, and when 3 moles of nitric acid per mole of alkyl sulfuric acid salts are initially present.

Example XI A mixture containing equal parts, by weight, of the sodium salts of C and C alpha olefine was added slowly, over a period of approximately 25 minutes, to an aque ous solution of nitric acid having a 30% concentration. The initial volume of the nitric acid solution was such that one mole of the alkyl sulfuric acid salt mixture was added per 7 moles of nitric acid at a rate which maintained the oxidation temperature at 100 C. During the oxidation, approximately 9 moles of additional 70% nitric acid were added per mole of alkyl sulfuric acid salts. The water-insoluble products, recovered as a fatty acidcontaining water-insoluble upper layer after termination of the oxidation and stratification of the reacted mixture exhibited an A.V. of 176, an H.V. of 58 and a nitrogen content of 1.46%.

The substitution of the sodium salts of C alkyl sulfuric acids derived from C alpha olefine in the process of this example results in the formation of monocarboxylic acids containing from 2 to 21 carbon atoms.

Example XII An aqueous slurry containing approximately 22% by weight of a mixture containing 30%, 38%, 25%, 6% and 1% respectively of the sodium salts of C C C C and C alkyl sulfuric acids derived from their respective alpha olefines was slowly added, over a period of 60 minutes, to an aqueous solution of nitric acid having an initial concentration of 30%. The nitric acid solution was preheated to a temperature of 85 C., and the alkyl sulfuric acid salt mixture was added at a rate which maintained this temperature. The initial volume of the nitric acid solution was such that one mole of alkyl sulfuric acid salt was added to 14.1 moles of nitric acid. An additional 25.5 moles of 70% nitric acid per mole of alkyl sulfuric acid salts was added to the reaction mass during the oxidation. A catalyst, consisting of 0.76% of vanadium pentoxide based on the weight of the alkyl sulfuric acid salts, was added to the aqueous solution of nitric acid prior to adding the alkyl sulfuric acid salts. The product, recovered as a fatty acid-containing water-insoluble upper layer after stratification of the reacted mixture, exhibited an A.V. of 184, an H.V. of 12 and a nitrogen conuse as sulfonated fatty acid detergents.

Example XIII An aqueous slurry containing approximately 40% by weight of the sodium salts of C alkyl sulfuric acid derived from C alpha olefine was added, over a period of minutes, to an aqueous solution containing 70% by weight of nitric acid. The initial volume of nitric acid solution was such that one mole of alkyl sulfuric acid salts was added per 16.4 moles of nitric acid at a rate which maintained the oxidation temperature at 107 C. A catalyst consisting of copper and ammonium vanadate employed in quantities of 0.84% and 0.21% respectively based on the weight of the alkyl sulfuric acid salts was added to the aqueous solution of nitric acid prior to adding the alkyl sulfuric acid salts. Mechanical agitation and refluxing were provided during the oxidation, but no additional nitric acid was added. The oxidation was terminated when gas evolution ceased, and the product, recovered as a fatty acid-containing water-insoluble upper layer after stratification of the reaction mixture, exhibited an A.V. of 276 and a nitrogen content of 2.26%. The molar yield of water-insoluble fatty monocarboxylic acid was 72% based on the moles of alkyl sulfuric acid salts entering the reaction.

Hydrolysis of the crude water-insoluble fatty monocarboxylic acids produced by the process of this example in an autoclave for 5 hours at 175 C. with an equal volume of 38% hydrochloric acid results in the extraction of approximately 90% of the nitrogen content.

When dimethyl sulfoxide is present as a solvent in the process of Example XIII, in an amount approximately equal to twice the weight of the alkyl sulfuric acid salts introduced, an increased percentage of the nitrogenous byproduct is retained in the water-soluble layer.

Example XIV Alkyl sulfuric acids derived from C alpha olefine were slowly added, over a period of 60 minutes, to an aqueous solution containing 30% by weight of nitric acid and preheated to 100 C. The initial volume of the nitric acid solution was such that one mole of the alkyl sulfuric acids was added per 12 moles of nitric acid, and the addition was made at a rate which maintained the oxidation temperature at 100 C. Copper-ammonium vanadate catalyst employed according to the process of Example I was used in this example. An additional 4.5 moles of 70% nitric acid per mole of alkyl sulfuric acids were added during the oxidation reaction to maintain the nitric acid concentration. Mechanical agitation and refluxing were provided and the oxidation was terminated after gas evolution ceased. The product, recovered as a fatty acid-containing water-insoluble upper layer after stratification of the reacted mixture, exhibited an A.V. of 189.7, an H.V. of 15 and a nitrogen content of 1.87%. The molar yield of water-insoluble fatty monocarboxylic acids was 67.2% based on the moles of alkyl sulfuric acids entering the reaction.

While preferred embodiments of the invention have been described, the descriptions are intended to be illustrative and it is to be understood that variations may be made without departing from the spirit and scope of the invention as defined by the appended claims.

What is claimed is:

1. A process for the manufacture of aliphatic monocarboxylic acids containing from about two to about twenty-one carbon atoms which comprises oxidizing and cleaving alkyl sulfuric acids, resulting from the sulfation of alpha olefines having about 8 to about 22 carbon atoms with nitric acid having a concentration of about 20% to about 92% in amounts to initially provide about 3 to about 20 moles of nitric acid per mole of said alkyl sulfuric acids and thereafter adding additional amounts of nitric acid up to a total maximum of 54 moles of nitric acid per mole of said alkyl sulfuric acids to maintain a nitric acid concentration of at least 20%, while maintaining the reaction at a temperature of about 50 C. to the reflux temperature of the reaction mixture until gas evolution ceases to form aliphatic monocarboxylic acids and recovering said aliphatic monocarboxylic acids by stratifying and separating the liquid reaction mass into a lower aqueous layer and an organic layer, wherein the nitric acid has an initial concentration of about 25% to about 35% and the aliphatic monocarboxylic acids formed are treated with hydrochloric acid having a concentration of about 20% to about 40%, at temperatures of about 175 C. to about 250 C., for about 2 to about 8 hours to remove nitrogen compounds 2. A process for the manufacture of aliphatic monocarboxylic acids having about 2 to about 21 carbon atoms which comprises the steps of adding aqueous slurries containing about 20% to about 60% by weight of alkyl sulfuric acids resulting from the sulfation of alpha ole fines having about 8 to about 22 carbon atoms to agitated, aqueous solutions having a concentration of about 25% to about 35% by weight of nitric acid and initially containing about 15 moles of nitric acid per mole of alkyl sulfuric acids together with about 0.54% of powdered copper and about 0.18% of ammonium vanadate based on the weight of the alkyl sulfuric acids, and thereafter adding additional nitric acid to maintain a nitric acid concentration of at least 20%, while effecting oxidation and cleavage of said alkyl sulfuric acids at a temperature of about C. to about C. until gas evolution ceases, recovering fatty aliphatic monocarboxylic acids from the reaction mixture by stratifying and separating the liquid reaction mass into a lower aqueous layer and an upper organic layer, and treating the fatty aliphatic monocarboxylic acids by hydrolysis with an equal volume of 38% hydrochloric acid for about 5 hours at about C. to remove nitrogen contaminants.

3. The process of claim 2, wherein the aqueous solution of nitric acid contains a maximum of about 65% of sulfuric acid.

4. The process of claim 2, wherein the copper-ammonium vanadate catalyst is replaced by a catalyst selected from the group consisting of copper, manganese dioxide, ammonium vanadate, benzoyl peroxide, vanadium pentoxide and cobaltic oxide, employed in amounts of about 0.005% to about 5.0% by weight of the alkyl sulfuric acids.

References Cited by the Examiner UNITED STATES PATENTS 1/ 1942 Czerwin 260-413 XR 9/1947 Sprules et al. 260-413 XR 

1. A PROCESS FOR THE MANUFACTURE OF ALIPHATIC MONOCARBOXYLIC ACID CONTAINING FROM ABOUT WO TO ABOUT TWENTY-ONE CARBON ATOMS WHICH COMPRISES OXIDIZING THE CLEAVING ALKYL SULFURIC ACIDS, RESULTING FROM THE SULFATION OF ALPHA OLEFINES HAVING ABOUT 8 TO ABOUT 22 CARBON ATOMS WITH NITRIC ACID HAVING A CONCENTRATION OF ABOUT 20% TO ABOUT 92% IN AMOUNTS TO INITIALLY PROVIDE ABOUT ALKYL SULFURIC ACIDS AND THEREAFTER ADDING ADDITIONAL ALKYL SULFURIC ACIDS AND THEREAFTER ADDING ADDITIONAL AMOUNTS OF NITRIC ACID UP TO A TOTAL MAXIMUM OF 54MOLES OF NITRIC ACID PER MOLE OF SAID ALKYL SULFURIC ACIDS TO MAINTAIN A NITRIC ACID CONCENTRATION OF AT LEAST 20%, WHILE MAINTAINING THE REACTION AT A TEMPERATURE OF ABOUT 50*C. TO THE REFLUX TEMPERATURE OF THE REACTION MIXTURE UNTIL GAS EVOLUTION CEASES TO FORM ALIPHATIC MONOCARBOXYLIC ACIDS AND RECOVERING SAID ALIPHATIC MONOCARBOXYLIC ACIDS BY STRATIFYING AND SEPARATING THE LIQUID REACTION MASS INTO A LOWER AQUEOUS LAYER AND AN ORGANIC LAYER, WHEREIN THE NITRIC ACID HAS AN INITIAL CONCENTRATION OF ABOUT 20% TO ABOUT 35% AND THE ALIPHATIC MONOCARBOXYLIC ACID FORMED ARE TREATED WITH HYDROCHLORIC ACID HAVNG A CONCENTRATION OF ABOUT 20% TO ABOUT 40%, AT TEMPERATURES OF ABOUT 175*C. TO ABOUT 250*C., FOR ABOUT 2 TO ABOUT 8 HOURS TO REMOVE NITROGEN COMPOUNDS. 